Spray gun for applying solid particles

ABSTRACT

A spray gun for applying solid particles to an article includes a handle and a barrel member. The passageway for conveying a suspension of solid particles in a carrier gas is an elongated flexible tube which extends from the spray nozzle through a bore in the barrel member, the handle and outwardly from the gun to the source of coating material particles. Such a gun can also include an elongated insulator forming a passageway for highvoltage circuit means within the gun and curved between the grip portion of the handle and another bore in the barrel. A closure means of insulating material at the front of the barrel can include a portion projecting into the barrel to provide electrical insulation for the connection between the high-voltage circuit means and an electrode mounted on the front of the spray gun. The closure means can also provide a means for attaching a spray nozzle at the front of the gun.

United States Patent [72] Inventors Richard 0. Probst;

Kenneth E. Pollard, both of Indianapolis, Ind.

[21] Appl. No. 833,352

[22] Filed June 16, 1969 [45] Patented Nov. 2, 1971 [73] AssigneeRansburg Electra-Coating Corp.

Indianapolis, Ind.

[54] SPRAY GUN FOR APPLYING SOLID PARTICLES 17 Claims, 2 Drawing Figs.

3,248,606 4/1966 Fraser 3,382,091 5/l968 Drum Primary Examiner-M. HensonWood, Jr. Assistant ExaminerMichael Y. Mar Attorneys-Merrill N. Johnson,Harry E. Downer, David H.

Badger and Charles W. I-Ioffmann zle through a bore in the barrelmember, the handle and outwardly from the gun to the source of coatingmaterial particles. Such a gun can also include an elongated insulatorforming a passageway for high-voltage circuit means within the gun andcurved between the grip portion of the handle and another bore in thebarrel. A closure means of insulating material at the front of thebarrel can include a portion projecting into the barrel to provideelectrical insulation for the connection between the high-voltagecircuit means and an electrode mounted on the front of the spray gun.The closure means can also provide a means for attaching a spray nozzleat the front of the gun.

PATENTEDNUV 2 ran mm ww m Om E iii wm mm mm 8 3 mm g wrmmm INVENTORSKENNETH E. POLLARI') RICHARD O. PROBST SPRAY GUN FOR APPLYING SOLIDPARTICLES BACKGROUND OF THE INVENTION This invention relates to animproved spray gun for applying solid particles and more particularly tosuch a gun which includes means to electrostatically charge such solidparticles for application.

Guns in common use for spraying and electrically charging solidparticles have included a barrel member of nonconducting material havingpassageways for the solid particles of coating material and for thehigh-voltage circuit components used to charge the solid particles. Someof these early guns have included a metallic handle member dependingangularly from the gun adjacent its rear to pennit an operator tosupport and manipulate the gun. in such guns the passageway for solidparticles was an integral portion of the gun and extended through thegun along a straight line. The conduit carrying solid particles to thegun was attached to the gun at its rear with a hose fitting. Where sucha gun included a grip portion dependent from the gun, the conduit wouldextend over the hand of the operator and, although flexible, wouldimpose forces on the hand of the operator which were fatiguing andrestrained the manipulation of the spray gun.

Other hand guns have been proposed having essentially a straight barrelto be used in a wandlike manner when manipulated by an operator. Fixedlysupported guns have been similarly arranged.

One such fixed gun, however, included a tube forming a passageway forsolid particles. A deflector for the solid particles was adjustablypositioned forwardly of the passageway. Means to adjust the deflectorextended along the passageway and rearwardly of the gun. The tubeforming the passageway was curved near the rear of the gun to provide aportion to which a conduit for solid particles was attached. The tubewas connected to a high-voltage source and was supported on a fixedholder in operation.

FEATURES OF THE INVENTION This invention provides a spray gun which ismore readily manipulated than any disclosed in the prior art. A gun ofthis invention includes as a passageway an elongated flexible tube fromthe spray nozzle at the front of the gun to the source of solidparticles to be applied. The spray gun includes a handle having a gripportion and a barrel. The elongated flexible tube forming a passagewayfor solid particles is curved to angle within the grip portion of thehandle and a bore in the barrel and terminates adjacent a spray nozzleat the forward end of the gun. In electrostatic spray guns, the barrelmember is of nonconducting material and includes, in addition to thebore for the elongated flexible tube, another bore. An elongatedinsulator is contained in this bore and curves within the grip portionof the device. The elongated insulator forms a passageway for highvoltage circuit means within the spray gun. At the front of such anelectrostatic gun, closure means is provided having two bores. Theclosure means includes a portion at its rear which extends into the boreof the barrel. One bore in the closure means accepts the elongatedflexible tube, and means is provided to attach a spray nozzle at thefront of the gun on the axis of this bore. The other bore is closed atits front end and accepts the elongated insulator. Means to electricallyconnect the circuit means in the elongated insulator with an electrodeat the front of the spray gun is carried within the closure means. Thepreferred embodiment of such a gun is shown in the attached drawings.

DESCRIPTION OF THE DRAWINGS FIG. I is a perspective drawing of a systemfor electrostatically charging and applying solid particles to articlesto be coated including a spray gun embodying this invention.

H6. 2 is a cross-sectional view through the center of the spray gun ofFIG. I.

DESCRIPTION OF THE PREFERRED EMBODIMENT Many coatings are moreadvantageously applied in dry powder form than as resins dissolved in aliquid carrier. Such coatings include those formed from pigmented resinsof polyethylenes, nylon, polyvinyl chloride and epoxides among others.FIG. 1 illustrates a method of applying such materials to an articleusing the apparatus of this invention.

Where thermoplastic or thermosetting powder material is to be applied toan article, the article in some instances is raised to a temperatureabove the fusion temperature of material but below the temperature atwhich the material is deleteriously aflected. The solid particles ofmaterial upon being deposited upon the article are fused into acontinuous film. In other instances where electrostatic charging isused, heating is sometimes unnecessary and the solid particles which aredeposited on the article are retained on the surface of the article as acoating of discrete particles by virtue of their electrostatic chargeuntil they can be fused.

Although articles of many configurations may be coated, the articles I0are illustrated in FIG. 1 as plates. Articles 10 are hung fromconductive supporting members ll depending from a conveyor 12, which ismaintained at ground potential. The articles 10 are electricallyconnected to ground potential by electrical contact with the conductivedepending members 11 and the grounded conveyor 12.

Solid particles of the coating material to be applied are placed in afluidized bed. This fluidized bed is formed in a source of coatingmaterial 13 for the spray gun 14. The source 13 includes a foraminousplate 15 forming the lower surface of the fluidized bed. Compressed airis supplied to an inlet 16 on the source of coating material 13. Thecompressed air is connected through a flow control regulator 17 (thedetails of which are not shown) to a chamber 18 within the source ofcoating material 13. Foraminous plate I5 forms the upper surface ofchamber 18. In operation, a flow of compressed air to chamber 18 iscontrolled by regulator 17. The air passes from chamber 18 through theforaminous plate I5 producing a fluidized bed of solid coating materialparticles, indicated as 19, within the source 13. An injection pump 20within the fluidized bed 19 is used to withdraw coating materialparticles from the bed for delivery to spray gun l4.

Compressed air from inlet 16 passes through flow control regulator 21(the details of which are not shown) and solenoid valve 22 (the detailsof which likewise are not shown). In operation a controlled flow of airpasses through regulator 21 and valve 22 into a nozzle within theinjection pump 20. The compressed air passing through the nozzle withinpump 20 creates a reduced pressure at an opening 23 of the injectionpump. Coating material particles are withdrawn from fluidized bed 19,entrained in the flow of compressed air and directed into an elongatedflexible tube 24.

Solid particles of coating material are conveyed suspended in thecompressed air through the elongated flexible tube into spray gun 14.Delivery of coating material to spray gun I4 is controlled by theoperator of the spray gun by manipulation of a trigger which actuatessolenoid valve 22, as will be explained. When the operator of the spraygun wishes to apply coating material particles to an article to becoated, he merely depresses the trigger of the spray gun. Coatingmaterial particles are withdrawn from source 13 in the manner describedand delivered through the elongated flexible tube 24 to spray nozzle 25on the spray gun. Actuation of the trigger also turns on a source ofhigh voltage 26. Electric charge is conducted through a high-voltageconductor 27 into spray gun l4. Coating material particles supplied tospray nozzle 25 are formed into a pattern suitable for application ofthe solid materials to the article to be coated. Solid particles emittedfrom the spray nozzle 25 are electrostatically charged by an electrode28 at the front of the gun and connected with the high-voltage conductor 27 within the spray gun 14. The spray nozzle can be changed whendifferent spray pattern is desired. Using such a spray gun, the operatorcan select the pattern most suitable for applying solid particles to thearticle to be coated and can easily manipulate the spray gun directing aflow of charged solid particles at the article to achieve a uniformcoating on the article.

Details of the regulators l7 and 21 to control the flow of compressedair are not shown since such regulators are in common use and theirselection can be made readily by one skilled in the art. An example ofsuch a regulator is Kendall Model 30 Air Pressure Regulator,manufactured by Fairchild- Hillor. Details of the solenoid valve 22 arelikewise not given. An example of such a valve is Skinner PrecisionIndustries, Inc. Solenoid Valve No. V30B2l00.

The structure of spray gun 14 which is the preferred embodiment of thisinvention, is shown in FIG. 2. The spray gun 14 includes a barrelincluding a barrel portion 29 attached to a handle 30 including a gripportion 31 depending at an angle below the barrel to provide a sprayoperator with means to grip and manipulate the spray gun. The barrelmember 29 is constructed of nonconducting material and includes twobores 32 and 33. Bores 32 and 33 have a short length at only the rear ofbarrel member 29 which is largely in the form of a relativelythin-walled tube.

An elongated insulator 34 forms a tubular passageway for circuit meanswithin the gun. The elongated insulator 34 is within bore 33 of thebarrel member 29 and is curved into the grip portion 31 of handle 30. Itis formed of nonconductive material, has a sufficient wall thickness towithstand high voltages, such as 50,000 to 100,000 volts, which areapplied to the gun, and provides a surface which will not act as a pathfor high voltage. Non conductive materials suitable for this applicationinclude for example, Delrin, nylon and polyethylene. Polyethylene is apreferred material for use as the elongated insulator since a wallthickness of about one-eighth inch will provide sufl'icient insulationagainst voltages of 50,000 to l00,000 volts and a surface of severalinches in length will resist sparking of these voltages over thesurface.

The elongated insulator 34 contains the end portion of the high-voltageconductor 27, which is a high-voltage cable of the type commonly in usein electrostatic coating apparatus, and a resistor 35 within the spraygun, preferably adjacent the forward portion of the barrel. The resistor35 is several inches long and is electrically connected to conductor 27with a small spring 36. The connection 36 between high-voltage conductor27 and resistor 35, the point of highest voltage within the spray gun,is thus well insulated from the handle and the forward portion of thegun. The elongated insulator 34 extends several inches rearwardly ofthis connection and is curved into the grip portion 31 of the handle.Angling the elongated insulator 34 from the barrel into the grip portionof the handle permits a shorter overall gun length. Resistor 35 is amultimegohm resistor having a typical value of 160 megohms.

The passageway for solid particles within the gun is formed by theelongated flexible tube 24. The elongated flexible tube 24 defines theentire passageway for conveying solid particles suspended in compressedair between the source 13 and the spray nozzle 25 at the forward end ofspray gun 14. The elongated flexible tube is inserted in the gripportion 31 of handle 30 and into the bore 32 of barrel member 29. Thehandle 30 contains means within it in the form of surfaces 37 and 38 tosupport the elongated flexible tube. Assembled within the spray gun, theelongated flexible tube curves between the grip portion 31 of the handleand bore 32 of the barrel.

The spray gun 14 at its forward end includes the closure means 39including a compression member 40 and an elastic member 41. Closuremeans 39 includes projecting portion 42 at its rear adapted to enter andbe fastened to the forward end of barrel member 29. Two bores 43 and 44pass through the projecting portion 42 at its rear in alignment withbores 32 and 33 respectively. Elongated flexible tube 24 passes withinbore 43 and compression member 40 to the forwardmost portion of closuremeans 39. Compression member 40 and closure means 39 are threadedlyengaged at the forward threaded portion 43a of bore 43. As compressionmember 40 is threaded into closure means 39, elastic member 41 iscompressed and grips elongated flexible tube 24 to fasten it withinspray gun l4.

Elongated insulator 34 is within bore 44 of closure means 39. Bore 44 isclosed at its forward end by closure means 39 which includes means 45,in the form of a small wire, electrically connecting the circuit meanswithin said elongated insulator to a surface in recess 46 at the forwardend of closure means 39. The forward end of closure means 39 alsoincludes a threaded portion 48 to provide means on the axis of bore 43for attaching spray nozzle 25 to spray gun l4. Spray nozzle 25 carriesan O-ring 47 in a groove to seal the spray nozzle with compressionmember 40. The rear surface of spray nozzle 25 carries a portion thatprojects into recess 46 when mounted on closure means 39. The electrode28 carried by spray nozzle 25 extends into the projecting portion of thenozzle and is electrically connected with the source of high voltage bycontacting electrical connecting means 45 within the recess 46 at thefront of closure means 39. Spray nozzle 25 and electrode 28 are attachedto the front portion of barrel 29 by a threaded nut of nonconductivematerial 49 which engages the threaded portion 46 of the closure means39.

Because of the arrangement of elongated insulator 34, closure means 39(particularly the projecting portion 42 at its rear end), and barrel 29,the electrical connection between the forward end of resistor 35 and theelectrical connecting means 45 of closure means 39 is prevented fromsparking to the operator's hand or other such grounded objectsapproaching the front portion of the barrel of spray gun l4. Elongatedinsulator 34 passes forwardly through bore 33 into closed bore 44 of theclosure member 49. semiconducting pluglike member 50 extends into thepassageway of elongated insulator 34 and contacts resistor 35 thusinterconnecting resistor 35 with the electrically connecting means 45 ofclosure means 39. Portion 42 ofclosure means 39, projects rearwardlyinto the barrel 29 a sufficient distance so that a circuitous path isformed over the surfaces of elements 34, 39, and 29 having a sufficientdistance to prevent sparking or other electrical leakage between theelectrical connection at element 50 and the outside of spray gun 14.Closure means 39 provides suffcient insulation thickness betweenpluglike member 50 and electrical connecting means 45 and its exteriorsurface to prevent sparking through the closure means to a groundedobject approaching the front of the gun. In like manner the recess 46 atthe front of closure means 39 permits the formation of a circuitous pathfrom the connection between electrode 28 and means 45 to the exterior ofthe spray gun 14 over the surfaces of elements 25, 39, and 48.

In the preferred embodiment, barrel member 29 of the barrel isconstructed of electrically nonconductive material. Materials suitablefor use in the barrel member include phenolic, epoxy, nylon, Delrin,polyethylene, polypropylene and other such materials. Barrel 29 may beformed by casting, injection molding, or machining of thesenonconductive materials. As shown in FIG. 2, the barrel member 29 isformed of a relatively thin-walled phenolic tube having a phenolicinsert 29a cemented in its rear that has been drilled to provide bores32 and 33. Closure means 39 of the barrel is likewise preferably formedof electrically nonconductive material. Materials identified as suitablefor use for barrel member 29 are also suitable for use for the closuremeans 39. As noted previously, the projecting portion 42 at the rear ofclosure means 39 is adapted to enter the barrel member 29. Use of abarrel like that comprised by composite barrel member 29 and closuremember 39 removes weight from the forward portion of the gun and permitsit to be economically made.

The elongated flexible tube 24 is preferably formed of a nonconductingmaterial such as nylon or polyethylene tubing. As a specific example, aspray gun like that shown in FlG. 2 would use a nylon hose having aninside diameter of threeeighths inch and an outside diameterofone-halfinch.

The handle 30 is preferably formed of a metallic material which can becast such as for example aluminum or zinc. The metallic handle ismaintained at ground potential by a braided conductor (not shown)forming the outside part of the cable used as the high-voltage conductor27. The braided conductor portion of high-voltage conductor 27 isconnected to the handle 30 and to a ground connection at the voltagesupply. The operator gripping portion 31 of handle 30 will, thus, bemaintained at ground potential and prevented from accumulating a staticcharge which might form a harmful uncontrolled electric discharge.

In operation, the operator depresses trigger 51 mounted on handle 30. Asthe trigger is depressed, a portion 52 extending into the handleactuates switch 53 contained within the handle 30. Conductors fromelectrical switch 53 (not shown) run through the grip portion of thehandle and are connected to voltage supply 26 (FIG. I) and solenoidvalve 22 (FIG. 1) in such a manner as to turn on the voltage supply andto open the solenoid valve when the trigger is depressed. Air flowingthrough injection pump thus entrains the solid particles of coatingmaterial from the fluidized bed 19 and directs it into the elongatedflexible tubing 24 forming the powder material passageway within thegun. The entire passageway from the injection pump to the spray nozzlehas a uniform cross section and a smooth wall without any discontinuity.Within the spray gun the elongated flexible tube curves graduallybetween the grip portion of the handle and the barrel. Thus, the coatingmaterial particles flow to the nozzle in a stable suspension. Inaddition, no solid particles are trapped in the passageway. The operatormay easily clean the passageway and in changing from one material toanother avoid contamination of the second material with a residue ofmaterials used earlier. The continuous passageway also prevents solidparticles from contaminating the interior of the spray gun withoutresorting to any seal members within the spray gun.

An advantage of this construction exists which is independent of use inan electrostatic gun. Where abrasive solid particles are applied, suchparticles flowing through a spray gun erode the passageway through whichthey pass.

This erosion is particularly troublesome if the coating passageway bendsas the particles due to their momentum will tend to impinge on the wallat such a bend. This problem was largely avoided where the coatingmaterial passageway did not curve into the grip portion of the handlebut extended rearwardly from the barrel along a straight line and passedout the rear of the gun over the hand of the operator. Attaching thesolid particle conduit in such a manner was unsatisfactory since thetubing through which coating material was delivered to the gun imposed atorquelike force on the spray gun which would fatigue an operator andrestrict the manipulability of the gun. As in the preferred embodimentillustrated in FIG. 2, the elongated flexible tubing, or the passagewayfor coating materials, can enter a spray gun at the base of the gripportion of the handle, a position where it imposes the least possiblerestriction on the manipulability of the spray gun, and curve into abarrel portion of the gun. in a sense, such a structure includes aself-contained and ready supply of replacement parts.

In the event of failure of the coating material passageway because oferosion of its walls by solid particles, the spray nozale and acompression member, like 40, can be removed from the front end of thegun. The elongated flexible tube which forms the passageway with itswalls, can be pushed or pulled forwardly through the spray gun and theportion of the tube containing the failure can be cut from the end anddiscarded. Replacing the compression member and elastic member at thefront of the barrel will fasten the elongated flexible tube to the gunand operation can be continued. This procedure can be repeated until theelongated flexible tube leading from the source of solid particlesbecomes too short to permit ready manipulation of the spray gun. Such aspray gun can thus be readily repaired many times without the delay ofobtaining spare parts.

While we have shown and described the preferred embodiment of ourinvention, it is to be understood that it is capable of manymodifications. Changes, therefore, in the construction and arrangementmay be made without departing from the spirit and scope of the inventionas disclosed in the following claims.

We claim I. An electrostatic spray gun for charging and depositingpowder particles comprising,

a handle including a grip portion,

a barrel of nonconducting material including two bores,

a closure means including a projecting portion at the rear and adaptedto enter the forward end of the barrel, and including two bores inalignment with the bores of the barrel,

an elongated flexible tube forming a passageway for powder particlesfrom the gun and angled to pass within the grip portion of the handleand one of the bores of the barrel and of the closure means,

an elongated insulator fonning a passageway for circuit means within thegun and angled to fit within the grip portion of the handle and theother of the bores of the barrel and the closure means,

said closure means including at its forward end a compression member onthe axis of the elongated flexible tube and threadedly engaging theclosure means, and means to grip the elongated flexible tube as thecompression member is threadedly engaged.

2. The electrostatic spray gun of claim I wherein the elongated flexibletube angled between the barrel and the grip portion of the handle formsa smooth curve.

3. The electrostatic spray gun of claim 1, including a spray nozzleattached to the closure means on the axis of the elongated flexible tubeand providing a seal with the compression member.

4. The electrostatic spray gun of claim I wherein the compression memberis a cylinder around the elongated flexible tube and threaded into theforward end of the bore carrying the elongated flexible tube, and themeans to grip the elongated flexible tube is an elastic member locatedin position to be compressed between the compression member and theclosure means as the compression member is threaded into the bore.

5. The electrostatic spray gun of claim I wherein the barrel includes abarrel member comprised of a thin-walled tube and an insert providingthe two bores.

6. An electrostatic spray gun for charging and depositing powderparticles comprising,

a handle including a grip portion,

a barrel member of nonconducting material including two bores,

a closure means including a projecting portion at the rear adapted toenter the forward end of the barrel and including two bores in alignmentwith the bores of the barrel,

an elongated flexible tube forming a passageway for powder particleswithin the gun and curved to pass within the grip portion of the handleand one of the bores of the barrel and of the closure means,

an elongated insulator forming a passageway for circuit means within thegun and gradually curved to fit within the grip portion of the handleand the other of the bores of the barrel and the closure means,

said closure means including at its forward end means for attaching aspray nozzle on the axis of the bore for said elongated flexible tubeand including means to electrically connect circuit means in the bore ofsaid insulator to a forward surface of the closure means.

7. The electrostatic spray gun of claim 6 including means at the forwardend of the closure means to fasten the elongated flexible tube withinthe spray gun.

8. The electrostatic spray gun of claim 7 wherein the means to fastenthe elongated flexible tube includes a cylindrical compression memberaround the elongated flexible tube and threadedly engaging the closuremeans.

9. The electrostatic spray gun of claim 8 including a spray nozzlemounted on the compression means, attached to the closure means, andproviding a seal between the compression means an the spray nozzle.

10. A gun for spraying solid particles, comprising,

a handle,

a barrel projecting from the handle and including a bore,

spray forming means attached to the forward end of the barrel,

an elongated flexible tube including a passageway for conveying solidparticles suspended in gas passing within the handle and the bore of thebarrel, the tube curving gradually in the gun,

means to fasten the elongated flexible tube with the gun, the

flexible tube adapted to be moved with respect to the gun when the tubeis unfastened from the gun,

the passageway of said elongated flexible tube being substantiallysmooth walled and having a substantially uniform cross section from asource of solid particles to the spray forming means whereby the solidparticles flow to the spray forming means in a substantially stablesuspension.

11. The gun of claim 10 including a cylindrical compression memberaround the elongated flexible tube and threadedly engaging the forwardend of the barrel, and means compressed as the compression member isthreadedly engaged to grip the elongated flexible tube.

12. The gun of claim 11 including a seal member between the cylindricalcompression member and the spray forming means.

13. The electrostatic spray gun of claim 6 wherein the elongatedflexible tube has a substantially uniform cross section from a source ofsolid particles to the spray nozzle whereby the solid particles flow tothe nozzle is a substantially stable suspension.

14. A spray gun for spraying solid particles comprising a barrelincluding a bore,

a handle including a portion depending at an angle from the barrel,

a spray nozzle adjacent to the forward end of the barrel,

an elongated flexible tube including a passageway for conveying solidparticles suspended in a gas within the portion of the handle dependingat an angle from the barrel and within the bore in the barrel, thepassageway of the flexible tube curving gradually in the handle toreduce erosion of the passageway at the curve by solid particles flowingthereby and the passageway having a substantially uniform cross sectionfrom a source of solid particles to the spray nozzle whereby the solidparticles flow to the nozzle in a substantially stable suspension.

15. The spray gun as claimed in claim 14 wherein a closure means isadjacent the forward end of the barrel and attaches the nozzle to theforward end of the barrel, the closure means engaging the elongatedflexible tube to locate the tube within the forward end of the barrel.

16. The spray gun as claimed in claim 14, wherein the barrel includestwo bores, the second of the bores including an elongated insulator forelectrical circuit means, the elongated insulator includes a curvedportion in the handle.

17. A spray gun for spraying solid particles comprising a barrelincluding a bore,

a handle including a portion depending at an angle from the barrel, and

means adapted to be moved with respect to the barrel, the

means including a passageway for conveying solid particles suspended ina gas within the portion of the handle depending at an angle from thebarrel and within the bore in the barrel, the passageway curvinggradually in the handle to reduce erosion of the passageway at the curveby solid particles flowing thereby and the passageway having asubstantially uniform cross section from a source of solid particles toa spray nozzle connected to the bore whereby solid particles flow to thenozzle in a substantially stable suspension.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3 ,617 ,000 DatedNovember 2 1971 Patent No.

Inventgr(s) Richard 0. PI'ObSt et al.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 3 line 13 "V3OB2100" should read V53OB21OO Column 4, line 33,"49" should read 39 Column 6, 1 ine I 7 "from" should read within Column7 line 4 "an" should read and Signed and sealed this 29th day of August1972.

(SEAL) Attest:

ROBERT GOTTSCHALK EDWARD M.FLETCHER,JR.

Commissioner of Patents Attesting Officer USCOMM-DC 60376-F'BQ MF'O-105O [IO-69] u 5 GOVERNMENT PRINTING ornc: Iss9 0-366-3Jl

1. An electrostatic spray gun for charging and depositing powder particles comprising, a handle including a grip portion, a barrel of nonconducting material including two bores, a closure means including a projecting portion at the rear and adapted to enter the forward end of the barrel, and including two bores in alignment with the bores of the barrel, an elongated flexible tube forming a passageway for powder particles from the gun and angled to pass within the grip portion of the handle and one of the bores of the barrel and of the closure means, an elongated insulator forming a passageway for circuit means within the gun and angled to fit within the grip portion of the handle and the other of the bores of the barrel and the closure means, said closure means including at its forward end a compression member on the axis of the elongated flexible tube and threadedly engaging the closure means, and means to grip the elongated flexible tube as the compression member is threadedly engaged.
 2. The electrostatic spray gun of claim 1 wherein the elongated flexible tube angled between the barrel and the grip portion of the handle forms a smooth curve.
 3. The electrostatic spray gun of claim 1, including a spray nozzle attached to the closure means on the axis of the elongated flexible tube and providing a seal with the compression member.
 4. The electrostatic spray gun of claim 1 wherein the compression member is a cylinder around the elongated flexible tube and threaded into the forward end of the bore carrying the elongated flexible tube, and the means to grip the elongated flexible tube is an elastic member located in position to be compressed between the compression member and the closure means as the compression member is threaded into the bore.
 5. The electrostatic spray gun of claim 1 wherein the barrel includes a barrel member comprised of a thin-walled tube and an insert providing the two bores.
 6. An electrostatic spray gun for charging and depositing powder particles comprising, a handle including a grip portion, a barrel member of nonconducting material including two bores, a closure means including a projecting portion at the rear adapted to enter the forward end of the barrel and including two bores in alignment with the bores of the barrel, an elongated flexible tube forming a passageway for powder particles within the gun and curved to pass within the grip portion of the handle and one of the bores of the barrel and of the closure means, an elongated insulator forming a passageway for circuit means within the gun and gradually curved to fit within the grip portion of the handle and the other of the bores of the barrel and the closure means, said closure means including at its forward end means for attaching a spray nozzle on the axis of the bore for said elongated flexible tube and including means to electrically connect circuit means in the bore of said insulator to a forward surface of the closure means.
 7. The electrostatic spray gun of claim 6 including means at the forward end of the closure means to fasten the elongated flexible tube within the spray gun.
 8. The electrostatic spray gun of claim 7 wherein the means to fasten the elongated flexible tube includes a cylindrical compression member around the elongated flexible tube and threadedly engaging the closure means.
 9. The electrostatic spray gun of claim 8 including a spray nozzle mounted on the compression means, attached to the closure means, and providing a seal between the compression means an the spray nozzle.
 10. A gun for spraying solid particles, comprising, a handle, a barrel projecting from the handle and including a bore, spray forming means attached to the forward end of the barrel, an elongated flexible tube including a passageway for conveying solid particles suspended in gas passing within the handle and the bore of the barrel, the tube curving gradually in the gun, means to fasten the elongated flexible tube with the gun, the flexible tube adapted to be moved with respect to the gun when the tube is unfastened from the gun, the passageway of said elongated flexible tube being substantially smooth walled and having a substantially uniform cross section from a source of solid particles to the spray forming means whereby the solid particles flow to the spray forming means in a substantially stable suspension.
 11. The gun of claim 10 including a cylindrical compression member around the elongated flexible tube and threadedly engaging the forward end of the barrel, and means compressed as the compression member is threadedly engaged to grip the elongated flexible tube.
 12. The gun of claim 11 including a seal member between the cylindrical compression member and the spray forming means.
 13. The electrostatic spray gun of claim 6 wherein the elongated flexible tube has a substantially uniform cross section from a source of solid particles to the spray nozzle whereby the solid particles flow to the nozzle is a substantially stable suspension.
 14. A spray gun for spraying solid particles comprising a barrel including a bore, a handle including a portion depending at an angle from the barrel, a spray nozzle adjacent to the forward end of the barrel, an elongated flexible tube including a passageway for conveying solid particles suspended in a gas within the portion of the handle depending at an angle from the barrel and within the bore in the barrel, the passageway of the flexible tube curving gradually in the handle to reduce erosion of the passageway at the curve by solid particles flowing thereby and the passageway having a substantially uniform cross section from a source of solid particles to the spray nozzle whereby the solid particles flow to the nozzle in a substantially stable suspension.
 15. The spray gun as claimed in claim 14 wherein a closure means is adjacent the forward end of the barrel and attaches the nozzle to the forward end of the barrel, the closure means engaging the elongated flexible tube to locate the tube within the forward end of the barrel.
 16. The spray gun as claimed in claim 14, wherein the barrel includes two bores, the second of the bores including an elongated insulator for electrical circuit means, the elongated insulator includes a curved portion in the handle.
 17. A spray gun for spraying solid particles comprising a barrel including a bore, a handle including a portion depending at an angle from the barrel, and means adapted to be moved with respect to the barrel, the means including a passageway for conveying solid particles suspended in a gas within the portion of the handle depending at an angle from the barrel and within the bore in the barrel, the passageway curving gradually in the handle to reduce erosion of the passageway at the curve by solid particles flowing thereby and the passageway having a substantially uniform cross section from a source of solid particles to a spray nozzle connected to the bore whereby solid particles flow to the nozzle in a substantially stable suspension. 